Fertility and Pupil Numbers A number of interesting findings emerge from these tables. One is that if fertility remains at its original, high level, it is only in the rather unrealistic situation in which the enrollment rate reaches the 95 percent target in 10 years that the rise in enrollment rates by itself is able to account for more than half of the increase in enrollments. In the more realistic situation in which 20 or 30 years are required to reach the goal, the rise in enrollments that is attributable to enrollment rate trends alone is much less. In the 30-year example only a quarter of the increase in enrollments can be attributed solely to the rise in enrollment rates, and this is exceeded by the rise caused by demographic trends alone (31 percent of the total increase) and by demographic trends and enrollment rate trends combined (42 percent). It is therefore unrealistic to treat demographic trends in a high-fertility country as only a marginal problem whose contribution to swelling student numbers is swamped by that of rapidly rising enrollment rates. In our specific example, unless the ambitious enrollment rate goals can be achieved in less than about 15 years, less than half of the increase in student numbers can be separated from the effect of population growth. When one looks at the time ahead only as a succession of short periods, instead of viewing the period in which the ER rises to its maximum as one unit, the contribution of both population trends per se and the ER increase per se to the increase in enrollments appears greater, and the component of the increase attributable to the interaction of the two factors, less. This can be illustrated by Table 10, which analyzes the situation in which it takes 30 TABLE 10 Disaggregation of Factors Underlying Enrollment Increase During Each 5-year Period When ER Rises from 40 Percent to 95 Percent in 30 Years in Hypothetical LDC: High Fertility Projection Percent Due to Demographic Rise in ER Both Factors Trends Alone Alone Combined 1st 5-year period 43.3 50.0 6.7 2nd 5-year period 44.7 48.3 7.0 3rd 5-year period 49.9 42.4 7.7 4th 5-year period 52.0 39.9 8.1 5th 5-year period 50.4 41.7 7.9 6th 5-year period 50.5 41.7 7.8 Entire 30-year period 30.9 26.6 42.5 Source: Author's calculations.